A Survey on Multi - Hop Cellular Networks

Wireless mobile communications technology has been evolving rapidly in the past decade. The number of mobile subscribers has reached 2 billions and is expected to reach 3 billions by the end of 2010. Most countries have already deployed or have started to deploy the third generation (3G) wireless cellular networks. In 3G, in addition to traditional voice service, users are provided with multi-media data services and a wide range of data rates up to 2 Mbps. Although high data rates are achieved, the inherent cell capacity and cell coverage limitations of these networks still exist. The capacity limitation raises the hot spot problem in a busy city centre or a large crowd situation such that many call requests are blocked. There is also the dead spot problem which occurs when signals between mobile users and base stations are blocked by obstructions. Recently, there have been proposals to apply the multi-hop relaying concept to existing cellular networks to enhance their capacity and coverage. We call these networks multi-hop cellular networks. As these networks consist of cellular and ad hoc components and, as a result, have their own issues and characteristics, designing a good multi-hop cellular network is a non-trivial task. In this survey, we first provide an overview of wireless networks including cellular networks and ad hoc networks. We then examine existing multi-hop cellular network proposals in terms of architectural design, medium access, routing, channel assignment and load balancing. Some open issues associated with these networks are also discussed.